That America has a weight problem can’t be denied, but the social perception that obese people simply can’t lose weight is not true, a new study finds.

According to researchers from the Beth Israel Deaconess Medical Center and Harvard Medical School in Boston, obese Americans are trying to lose weight — and many are successful. The researchers looked at data for 4,021 obese people ages 20 and older who participated in the government’s National Health and Nutrition Examination Survey. Between 2001 and 2006, about 63% of those participants were trying to lose weight, and 40% slimmed down — losing at least 5% of their body weight. Twenty percent of the participants lost 10% of their body weight or more.

“I was surprised by how many people in our study had success,” says lead researcher Dr. Jacinda Nicklas, a clinical research fellow at Beth Israel Deaconess Medical Center and Harvard Medical School. “We have this impression that it is really difficult for obese people to lose weight, but no, they are losing weight. Even if it’s a modest amount, you don’t have to be thin to have a nice health effect.”

Clinical guidelines recommend a loss of 10% of body weight for obese adults to improve their health, but according to Nicklas, studies have shown that even a 5% loss of body weight has measurable health perks.

How did the successful losers do it? Here’s what didn’t work: using fad techniques like 30-day liquid cleanses, taking nonprescription diet pills and eating “diet” foods. Obese Americans who reported weight loss were more likely to steer clear of the so-called latest and greatest in dieting and instead adopt the classic technique of eating less and exercising more, reporting that they “drank lots of water” and “ate less fat,” for example.

The most popular strategies were eating less, exercising more, eating less fat and switching to lower-calorie foods. People who used commercial weight-loss programs and prescription weight-loss pills also saw success, but only a small portion of the study participants used them. Meanwhile, liquid diets, nonprescription diet pills and popular diets showed no association with weight loss.

“It’s reassuring that patients are using the less costly strategies that have been shown to be effective and the more ‘tried and true’ strategies,” says study author Dr. Christina Wee, co-director of research at the Division of General Medicine and Primary Care at Beth Israel Medical Center. “I think what is also reassuring is that when they try, in general, they lose weight.”

Participants who lost more (at least 10% of their body weight) were more likely to have joined a commercial weight-loss program — they tend to keep dieters more accountable — and were less likely to report eating diet foods.

“If you look at the people trying to lose weight, using diet foods and products was actually detrimental to weight loss. We call it the ‘health halo’ effect,” says Nicklas. “When a food is labeled as diet or low fat, people think that eating it will make you lose weight. So they end up eating a lot more than they should.”

The researchers found that prescription weight-loss pills were most strongly associated with weight loss but that only a small number of participants reported using them. Wee speculates that doctors may be hesitant when it comes to prescribing diet pills. “I think there is a reluctance on the side of the health providers for prescribing these, and some are well justified. Some prescription pills have later been found to be harmful. We also know from other studies that sometimes there is not a lot of time for weight counseling during appointments. Patients are getting a lot of their weight-loss advice from elsewhere, and take it upon themselves to lose weight. They may be less engaged with their physician in that.”

Of course, dropping pounds is only half the battle. Keeping it off long-term is often the hardest part, which is why the research team calls for further studies to identify the barriers to maintaining weight loss. “We haven’t taught people how to maintain,” says Nicklas. “That’s the biggest challenge. There is a problem with maintaining weight, and we need to better educate people on how to do this.”

The study was published in the American Journal of Preventive Medicine.